Thermostat

I was just thinking about this , when motor is cold & just idling poppet valves are closed . water heats up to thermostat temp it , opens & lets the hot water out more cold water comes in it closes because i assume the temperature changes because the impeller pumps more cold water in & a thermostat closes in temp change this cycle gets repeated .
now you ready to go
you throttle up to say 1\2 the impeller rpm increases pumps water faster pressure inside motor builds up poppet valves open cold water continually flows through the motor & yet the thermostat in my 70hp is right next to poppet valves in the same pool of water & the cold water coming in faster flowing through the motor straight out right next to the thermostat
this tells me its closes because of temp change , see my point
unlike a car where there is no supply of cold water because the water coming out of the radiator not 'cold'
how long does it take for water of a large volume to reach whatever temperature your thermostat is designed for when there is a constant supply of cold water that does not stay in one place long enough to get to what ever temp

the way i see it that ist only there for start up from cold , i could be wrong just my way of thinking .buy me fitting a temperatur gauage i need the temp of the block & not the water

Re: Thermostat

You are wrong.
To obtain a complete combustion you need 3 parts:temperature - carbon and oxygen. Roughly look at is as a birthday cake split in 3. If one piece gets smaller, you have to make another bigger to still have a complete cake.
To obtain a clean combustion at as low temperature as possible, you increase temp and lower the carbon piece. normally the limit of temp increase is around 64C due to salt deposits/crystallization from sea water. So to keep a smooth and 'clean' idling and low rpm, you increase temp and have a low fuel consumption. However power is a function of how much carbon (fuel) you may burn. To get max power, you INCREASE amount of fuel, but at the same time you need to lower the temp to keep the 'cake' complete!! This is where the poppet valve comes into play. If hooking a temp gauge to an outboard where the cooling system is working according to factory spec, you may notice that on most engines it drops from around 3500 rpm to around 50C.
To further illustrate, starting a cold engine you normally need a choke/primer to add fuel to compensate for lack of temp. The low and intermediate systems in the carbs are metered out for optimum at correct temp.
If running a constant temp without the poppet valve and lower temp at full speed, the high speed jet must be reduced for the engine not to run rich, which means loss of power.
You may need some ice cubes in your laundry machine circulation system to be injected at higher rpm??

Re: Thermostat

my laundry machine cooling system my just tag on one day so you can go fishing in the mud , like the one fella i saw on goggle , ha , thanks for your share of the cake , i do things practically to prove my point , cheers m8t
drill & tap a hole in the thermostat cover & fit a tube there den you see my point ,

Re: Thermostat

How about adding a car air-con pump, belt driven from your epoxy 'light weight' flywheel with cooling tubes down in the laundry machine? Then with a valve hooked up to the throttle lever you might be able to get a simulation of the poppet valve????? Could even add and electric clutch so it does not take power at idle?

Re: Thermostat

no i have one better , what about a turbo charge , or build a Johnson helicopter cause all we have to do is turn the motor upside down turn the carbs around fit my laundry cooling system & blades to the shaft & away we go

Re: Thermostat

Haffiman said:

You are wrong.
To obtain a complete combustion you need 3 parts:temperature - carbon and oxygen. Roughly look at is as a birthday cake split in 3. If one piece gets smaller, you have to make another bigger to still have a complete cake.
To obtain a clean combustion at as low temperature as possible, you increase temp and lower the carbon piece. normally the limit of temp increase is around 64C due to salt deposits/crystallization from sea water. So to keep a smooth and 'clean' idling and low rpm, you increase temp and have a low fuel consumption. However power is a function of how much carbon (fuel) you may burn. To get max power, you INCREASE amount of fuel, but at the same time you need to lower the temp to keep the 'cake' complete!! This is where the poppet valve comes into play. If hooking a temp gauge to an outboard where the cooling system is working according to factory spec, you may notice that on most engines it drops from around 3500 rpm to around 50C.
To further illustrate, starting a cold engine you normally need a choke/primer to add fuel to compensate for lack of temp. The low and intermediate systems in the carbs are metered out for optimum at correct temp.
If running a constant temp without the poppet valve and lower temp at full speed, the high speed jet must be reduced for the engine not to run rich, which means loss of power.
You may need some ice cubes in your laundry machine circulation system to be injected at higher rpm??

Click to expand...

funny enough when the japanese bought out the 2 stroke Suzuki GS 750 - 1000 cc in the early 70ties with 3 pistons & a radiator i wonder why they never put any ice cubes in the system . makes you think aye

Re: Thermostat

durban said:

I was just thinking about this , when motor is cold & just idling poppet valves are closed . water heats up to thermostat temp it , opens & lets the hot water out more cold water comes in it closes because i assume the temperature changes because the impeller pumps more cold water in & a thermostat closes in temp change this cycle gets repeated .
now you ready to go
you throttle up to say 1\2 the impeller rpm increases pumps water faster pressure inside motor builds up poppet valves open cold water continually flows through the motor & yet the thermostat in my 70hp is right next to poppet valves in the same pool of water & the cold water coming in faster flowing through the motor straight out right next to the thermostat
this tells me its closes because of temp change , see my point
unlike a car where there is no supply of cold water because the water coming out of the radiator not 'cold'
how long does it take for water of a large volume to reach whatever temperature your thermostat is designed for when there is a constant supply of cold water that does not stay in one place long enough to get to what ever temp

the way i see it that ist only there for start up from cold , i could be wrong just my way of thinking .buy me fitting a temperatur gauage i need the temp of the block & not the water

Click to expand...

The engine designers say that a motor must reach operating temp for the combustion to operate properly , with the impeller constantly pumping cold water in & circulates through the motor pumping straight out with continues flow of cold water coming in , surely the block temp drops & the thermostat being in the same pool of water ,closes i can understand when the motor is idling that water in the motor stays in because poppet valves are closed due to no cold water pressure because rpm is only at idle , when it heats up thermostat opens & out it goes when you throttle up rpm increases cold water coming in faster temperature changes ,
this has got me thinking when it comes to operating temp , is the motor running at the correct temperature for efficient gas to form at the correct temperature petrol peaks\explodes ,

Having said all this , i have noticed a change in motor performance running with a closed loop water system .

before you answer have a look at spark plugs a motor that runs under peak & correct operating temp , THE PLUGS SHOULD BE BROWN\greyish IN COLOUR

Re: Thermostat

I am confused on this subject too, so maybe some of you can enlighten me to this similar situation of mine. I have a Johnson 150 Fast Strike (6 cylinder) which has two thermostats. One on each side of the engine. We noticed that one side of engine(left) was warmer to the touch than the other, so we took out that thermosat for inspection. The thermosat looks like an acorn, with the hat piece threaded into it's base, and is spring loaded. This "hat' part was threaded down crooked, so I took a screwdriver tip and gently pryed it to try and level up the acorn hat part. As a result, the edge of the inside threading sheared off, and the thremostat won't hold together now. No biggy. I headed to the local boat joint and found out that this thermostat was disncontinued, and has been replaced with one with a different design. It came complete with it's own new covering cap, spring and all. So I installed it and ran the engine to smooth idle with muffs on (pissing well, excellent water flow). The water discharge was cool, but the new stat side was even hotter than when I had the old stat in? I am concerned if the new stat is not working porperly, or has a higher temp opening point? I did a fail safe check on the stats, thinking maybe it could be an engine side to side issue. So I swapped the new stat to other side of the engine (right side which has the temp sensor just below the stat) and that side got hot and the left side became cool with the old, undamaged stat. Any and all advise would be appreciated.

Re: Thermostat

As long as the are the correct replacement, they should be fine. Maybe your old 'stat is opening at a too cool temp? Did you double check for the orig. replacement at crowleymarine web Site?

Re: Thermostat

How hot is the "hot" side? Can you find out?
Thermostats often degrade over time and opening too cool is the typical behaviour for an old stat. In fact I've never seen a 20 year old stat still working perfectly, no matter whether in a car or an outboard engine. So I guess both of your stats are bad and the "hot" cylinder bank with the new thermostat has the correct temperature.

Re: Thermostat

Two 'mistakes':
1: Thermostats are changed as 'pairs' and in particular if of different designs.
2: never test temp and cooling on muffs, but either launch the boat or use a barrel/drum filled with water min 3 inch above the split between gear case and leg.

Re: Thermostat

WernerF said:

How hot is the "hot" side? Can you find out?
Thermostats often degrade over time and opening too cool is the typical behaviour for an old stat. In fact I've never seen a 20 year old stat still working perfectly, no matter whether in a car or an outboard engine. So I guess both of your stats are bad and the "hot" cylinder bank with the new thermostat has the correct temperature.

Click to expand...

This is what I came up with too after sitting and thinking about it a bit. I just went ahead and repalced the other side too. I guess the engines are supposed to run better when they are warmer than what the old thermosats governed them to operate at. My thinking, which the boat joint confirmed, was it would be better to have both sides running at app the same temp instead on one hot and one cold. Thanks for the responses.

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